The spectrum for 5G/NX systems is generally expected to be allocated in higher frequency bands than the spectrum for today's cellular systems, even in the millimeter wave region. At these high frequencies, the propagation conditions, in terms of attenuation, penetration and refraction, are not as favorable for wireless communications as the lower frequencies utilized today. To overcome these problems, 5G/NX systems are assumed to rely heavily on beamforming in order to more efficiently direct the radiated energy towards the intended receiver. This has the great advantage that the coverage area can be increased, but it is also associated with problems, since the reliance on beamforming prevents an access node from reaching its entire intended coverage area, unless access nodes are deployed densely enough to compensate for the poor propagation conditions.
Because of the above circumstances, an access node transmitting a signal may transmit the signal using a single omnidirectional transmission, transmit it using a few consecutive wide beams, which together covering the entire coverage area, or using a potentially great number of consecutive narrow beams. In the general case, multiple consecutively transmitted narrow beams can be assumed to be used, this is referred to as a beam sweep.
Discontinuous Reception, DRX, is a possible way to enable a wireless communication device to save energy by staying in a low-power sleep mode most of the time and only wake up to receive certain signals, such as signals carrying tracking area information, monitor paging occasions and perform measurements.
Having as short awake periods as possible is crucial to make the DRX efficient and the energy consumption low. In the context of e.g. reception of tracking area information, short awake periods can be achieved if the occasions when the signal is transmitted are well defined. However, in the case where this information is transmitted using beam sweeps, the time to receive the signal is inherently vaguely defined, because it is unknown which of the beams in the beam sweep the wireless communication device will be able to receive. The result is that the signal transmission/reception occasion is extended to a longer time window that covers the entire beam sweep duration. Hence, because of the need for beam sweeping, the awake time periods when using DRX become much longer than required for reception of a single transmission. This can potentially severely degrade the performance of the DRX and significantly increase the energy consumption, which is especially unfavorable for energy deprived devices, such as many MTC devices, e.g. sensor devices.
The proposed technology aims to provide counter measures to the interconnected problems of beam sweep transmissions and energy deprivation of potentially receiving devices. It aims in particular to provide mechanisms whereby a wireless communication device can save energy, or power, and at the same time receive information transmitted to the device using beam sweep transmissions.